Caulk around the entire exterior of the window frame, fill in any gaps between the window and siding.If you have casement/awning windows run a bead around where the window seats into the frame. Sliders same thing, run a bead around the outside of the window and track. In the case of the mold,you will have to expose more around the window because you don't know where it is leaking from and how much mold there actually is. It could be halfway up either side of the window or even started from the top for that matter.Vapor barrier and all affected insulation needs to be removed.After removing all the affected material, you then need to saturate the framing with a solution of bleach and water about 60/40,then let sit for 8 to 10 hours depending on how much mold there was.